SULAYMANIYAH, Iraq – When Ali Anbori heard about the killing of his friend and colleague Ahmed Shaker, a professor at the University of Baghdad last week, he recalled how he himself has been the target of death threats during the past few years.

"Someone put a piece of paper under my door and it said, 'you have to be careful. This is the last warning and next time it won't be a warning, we will execute you and your children,'" he recalled of the latest threat.